This invention relates to optical waveguide lasers and amplifiers and, in particular, to waveguide lasers and amplifiers having enhanced thermal stability.
Optical waveguide lasers and amplifiers are important components in optical communication systems. They are critical components in transmitters, receivers and intermediate amplifiers. It is important that the lasers and amplifiers in such components be stable in both wavelength and power.
A typical waveguide laser or amplifier comprises a length of glass optical fiber doped with one or more rare earth dopants such as erbium and/or ytterbuim. The doped fiber has an absorption band due to the rare earth dopants, and it is pumped by light from a plurality of semiconductor light emitters such as light emitting diodes. The efficiency of the laser or amplifier depends on the overlap between the absorption band of the fiber and the output spectra of the pump emitters.
A difficulty with waveguide lasers and amplifiers in communication systems is their sensitivity to changes in temperature. As the emitters heat up, their output spectra shift to higher wavelengths. At the same time, their output powers decrease. These variations change the laser or amplifier output power and the response of the transmitter or receiver employing them. Accordingly there is a need for waveguide lasers and amplifiers having enhanced thermal stability.
In accordance with the invention, a waveguide laser or amplifier having a peak absorption wavelength is provided with pump emitters having wavelengths deliberately offset from the peak absorption wavelength. The offset wavelengths of the emitters are chosen to enhance the thermal stability of the laser or amplifier. In one exemplary embodiment, the laser or amplifier having a peak absorption is pumped by a bimodal distribution of emitters having output peaks on the short wavelength side and the long wavelength side of the waveguide absorption peak.